Field of the Invention
The invention relates to a power switch (breaker) that is connected in a current path between connections of a supply voltage, and has switching devices for overload protection.
Power switches are connected in series with a load between the terminals of the supply voltage in order to switch the supply voltage to the load. It is necessary to protect the power switches against overloading in order to prevent destruction resulting from excessive heat losses. It is particularly critical if a short occurs in the load and virtually the entire supply voltage is present across the power switch.
Measures for short-circuit protection of a power switch that is operated cyclically is disclosed in Published, Non-Prosecuted German Patent Application DE 39 36 544 A1. An input signal that controls the switching transistor is delayed by a constant delay time. The delayed control signal disconnects the power transistor that is switched on the occurrence of an overvoltage condition caused by a load short.
In addition, the power transistor is disconnected when an overtemperature condition is detected by a temperature sensor that is thermally coupled to the power transistor.